This invention relates generally to the testing of electronic apparatus and is particularly directed to a high voltage test chamber for testing electronic components and modules.
The high speed testing of electronic components is commonly used to ensure quality control in production runs. Each component is typically subjected to at least one test procedure, and frequently more, in order to determine its electrical characteristics under various operating conditions. For example, the leakage current within a diode across which is applied a predetermined voltage may be measured for determining the blocking characteristics of the diode. The charge capacity of a capacitor or the resistance of a resistor may be measured with a given voltage applied thereacross in accepting or rejecting the components in a production lot. The tendency today is for increased production lot testing in the form of more individual component tests as well as the high speed testing of increased numbers of components within a given production lot for ensuring higher component reliability.
In order to prevent arcing, a dielectric medium is typically provided within the test chamber to reduce an electric field in the space between the electrodes across which the high voltage is applied and with which the electronic component is placed in circuit. Prior art approaches have generally made use of a dielectric in liquid form for providing this isolation. The use of a liquid dielectric, while providing desirable electrical characteristics in the test chamber, generally complicates the test procedure. For example, following submersion in the liquid dielectric, the dielectric must generally be removed from the surface of the component, generally by means of a drying process or a rinse-and-dry process. This involves additional components, e.g., a heater and/or a blower, in the test procedure. Since this drying process is typically accomplished outside of the test chamber, the liquid dielectric or rinse solvent which evaporates from the components is lost and generally enters the atmosphere. In addition, submersion of the components within the liquid dielectric and their removal from the test chamber results in additional dielectric loss as some of the liquid dielectric remains upon the components and is removed from the test chamber. The loss of liquid dielectric by either of the aforementioned causes is not only undesirable from an environmental standpoint, but also is economically unacceptable particularly where relatively expensive dielectric materials such as Freon and various fluorinated hydrocarbons are utilized.
Finally, prior art approaches utilizing liquid dielectrics suffer from limitations arising from spurious electric leakage currents, particularly from contamination of the dielectric. These contaminants may be carried and introduced into the dielectric liquid by the electronic components themselves. Once suspended in the liquid dielectric, its high voltage leakage current characteristics become irregular and unpredictable resulting in reduced test result reliability. Perhaps the most bothersome contaminant is water which can enter the test chamber by various means and which can substantially change the voltage isolation characteristics of the dielectric material.
The present invention represents an improvement over the prior art by providing a high voltage test apparatus for electronic components wherein an electrically inert vapor is continuously circulated through a test chamber to prevent arcing and stray electrical currents therein during the testing of a component. The present invention maintains contaminants within the test environment to a minimum, virtually eliminates loss of the dielectric vapor from the test apparatus, and eliminates arcing and stray currents within the test chamber even at very high test voltages to permit the accurate measurement of even very small currents within the component under test.
Objects of the Invention
Accordingly, it is an object of the present invention to provide an arrangement for the safe, accurate and high speed testing of electronic components and modules under high voltage conditions.
It is another object of the present invention to provide a high voltage electronic component test arrangement having a closed, circulating dielectric vapor system for reducing the possibility of electrical arcing and for minimizing leakage currents.
Yet another object of the present invention is to provide a high voltage test arrangement for electronic components utilizing a dielectric medium which substantially reduces sources of inaccurate measurements arising from dielectric contamination.
A further object of the present invention is to provide a high voltage test chamber particularly adapted for the automatic, high speed testing of electronic components.
A still further object of the present invention is to provide a test environment for testing electronic components under very high voltage conditions, e.g., greater than 20 kilovolts, wherein extremely small currents, e.g., on the order of nano-amperes, may be accurately measured.